Bag making apparatus



United States Patent [72] Inventors John Gunyou; 3,160,690 12/1964 Schaieh 93/59 Charles E. Wright, Toronto, Ontario, 3,237,367 3/1966- Fievet 93/94 Canada 3,303,760 2/1967 T0bias.. 93/94 [2]] Appl. No. 791,590 3,346,435 10/1967 Beck 156/69X [22] Filed Jan. 16, 1969 3,354,601 11/1967 Schneider.... 53/28 [45] Patented Nov. 17, 1970 3,354,603 11/1967 Katzcw.... 156/69X [73] Assignee E. S. & A. Robinson (CanadalLimited, 3,354,795 1 H1967 Kugler 93/33 Toronto, Ontario, Canada 3,364,825 H1968 Baumgartner 93/59 3,395,622 8/1968 Kugler 93/35 541 BAG MAKING APPARATUS FORE'GN PATENTS 13 Claims, 10 Drawing Figs. 1,160,721 12/ 1960 Germany 156/69 [52] U.S. Cl 93/20, Primary ExaminerWayne A. Morse, Jr.

93/26, 93/33. 93/35, 93/55. 1 93/82; 156/69 Attorney-Stevens, Davis, Miller and Mosher [51] lnt.'Cl B3lb l/08, B31b1/16,B31b43/00 [50] Field ofSearchmr 93/20, 26, ABSTRACT: An apparatus f continuous manufacture of 33(all), 35(RB), 39.1(P), 55.1(P), 59( L 82, thermoplastic bags having limp sidewalls and a semirigid base 94(PX); l56/69 which will have free-standing properties both when full or em ty, from flat webs of thermo lastic materials with dif- [56] References Cmd fer nt thickness or density wherein means for forming in situ UNITED STATES PATENTS the heavier material into a semirigid base, means for forming 1,962,213 6/1934 Reed 93/59 the lighter material into an elongated tube, means to bring the 2,704,179 3/1955 Wilcox. 93/55.l tube into contact with the formed base, means to heat seal the 2,896,387 7/1959 Brock... 93/59 tube to the base and means to sever the formed bag from the 3,090,157 9/1961 Ollier 93/55.1 web of heavier material and from the tube are provided.

Patented Nov. 11, 1970 3540355 Sheet 1 Of 6 his- Patented Nov. 17, 1970 Sheet 3 or 6 n li I l l FIG.6

Patente Nov. 17, 1970 3,540,355

Sheet 4 of 6 FIG? Patented Nov. 17, 1970 3,540,355

Sheet 5 or 6 Patented Nov. 17, 1970 3,540,355

Sheet 6 or 6 96 l 99 7 1 I 64 1 I L I v 1! III! I l l z I ll ll i1 1/ lll l I 1/1) AH! I l' I BAG MAKING APPARATUS This invention relates to an apparatus for forming bags of thermoplastic material or material having at least one side which is heat-sealable thermoplastic. In particular, the present invention provides an apparatus for forming a normally limp thermoplastic bag with a column-shaping bottom wall more rigid in nature than the sidewall that imparts substantial freestanding properties to the normally limp bag as a whole whether it is in a loaded or unloaded condition. difficult It is presently known to provide bags that are substantially free standing when such bags are in a loaded condition. For example, rectangular bottomed bags ofthcrmoplastic material are manufactured which, when loaded with sugar, flour or the like, benefit from a flnt bottom of substantial area which retains a bag in upright position. The retention oltheir upright position when loaded is accomplished by the weight of the contents spreading the flexible material of the bottom into conformity with the upholding surface such as a shelf or the like. However, it is extremely difficult to load such bags with produce because, in an empty or unfilled condition, the sidewalls tend to cling together in collapsed form and the bags easily will fall over on the loading line. Devices must therefore be provided to retain the bags in proper relationship to the product-loading mechanism. This known type of bag is often difficult to unload also due to the fact that, when the bag is inverted so that the contents may be released, the bottom of the bag as well as the sidewall structure adjacent thereto easily collapses to trap portions of the produce within the bag.

The addition of a column-shaping rigid bottom does not remove from the bag the inherent collapsing properties for shipping purposes and the formed bag, in its free-standing position, is easily loaded with produce whereby the inclusion of mechanism on a production loading line for holding the mouths of the bags open may be obviated. Accordingly, then, the bag could be manufactured prior to and in conjunction with loading to take advantage'of thiscondition.

In order to impart the above-mentioned column shaping to the wall structure of a thermoplastic bag, the bottom wall material is of a more rigid nature than the sidewall material. As applied in the present application, the term rigid" may be defined as (a) a bottom wall that is more dense or thicker in gauge than the material of the associated sidewall structure; (b) the particular shape of the bottom wall, i.e., the use of rigidifying ribs or the like; and (c) a bottom wall of the same weight as the sidewall structure, but being of higher density in molecular structure. Accordingly, a bag having a bottom wall that is rigid in structure and which is column shaping in respect to its associated sidewall provides an easily shelf-storable item from which contents may be gradually and easily removed without precollapsing ofthe bag adjacent its bottom wall. Moreover, such a bottom wall causes the associated flexible sidewall to retain a cross-sectional tubular shape corresponding to the annular or peripheral configuration of the bottom. Such a bag is described in U.S. Pat. No. 3,354,601 to Schneider et al. issued Nov. 28, I967.

According to one aspect of the invention there is provided an apparatus for manufacturing thermoplastic bags having a bottom wall more rigid in nature than its associated sidewall, comprising a forming mandrel adapted to receive therearound a first web of thermoplastic film to form a tubular sidewall structure for said bag; a female mold resiliently mounted for limited axial movement in one end of said forming mandrel; a male mold mounted in juxtaposition with respect to said female mold, and being adapted to deform and press a portion of a second web of material into said female mold and into peripheral engagement with one end of said sidewall structure; means for reciprocating said male mold toward and away from said female mold; and annular cutoffmeans adapted, when actuated, to sever said second web from the portion within said molds and simultaneously to heat seal said portion to said sidewall structure thereby to form said bottom wall.

The apparatus of the present invention is particularly useful in carrying out the method of making rigid-bottomed plastic bags described in our U.S. Pat. application No. 791,572 filed Jan. 16, 1969 and assigned to a common assignee.

The invention is illustrated by way ofexample in the accompanying drawings in which:

FIG. 1 is a perspective view of a bag made on the apparatus of the present invention in a loaded state;

FIG. 2 is a view similar to FIG. I but showing the bag in an unloaded state in a free-standing position;

FIGS. 3 and 4 are schematic illustrations in elevation and plan views respectively of a portion of one embodiment of the apparatus of the present invention for performing the sidewall structure of the bag before the bottom wall is applied thereto;

FIG. 5 is a schematic cross-sectional view of another portion of the apparatus of FIGS. 3 and 4 for applying the rigid bottom wall to the sidewall structure ofthc bag;

FIG. 6 is a more detailed illustration in elevation ofthe bottom-forming and applying apparatus of the embodiment shown in FIGS. 3-5 showing cutoff means for carrying out severing and sealing operations on a formed bug;

FIG. 7 is an illustration in elevation of the cutoff means shown in FIG. 6;

FIG. 8 is a schematic cross-sectional view of an alternative embodiment-of the apparatus with the die closed for heat sealing the side walls'to the rigid base;

FIG. 9 is a schematic cross section of the embodiment of FIG. 8 with the dies open; and

FIG. 10 is a schematic cross section of a further embodiment for heat sealing and severing the bags.

As shown in FIG. 1, a flexible bodied bag 10 is formed from a heat scalable material such as thermoplastic and is loaded with a substance 12 such as sugar. Bag 10 is provided with a tubular or columnar sidewall structure 14 also formed of thermoplastic material such as polyethylene or a material ofwhich one surface is thermoplastic such as plastic-coated paper. Polyvinylidene chloride is an example of a suitable coating. Connected to the lower end of the sidewall structure I4, for example by heat sealing, is a substantially flat bottom wall I6 of traylike configuration having an annular flange or bead l7 thereon. It will be appreciated that, in plan view, the bottom wall can be oval, square, rectangular or any polygonal shape although round or square is the preferred configuration for I6 is more rigid innature'than the material of the sidewall I4 which imparts a column-shaping influence to the sidewall structure, the form of which is substantially retained even when the bag is in an unloaded or partially unloaded state as shown by FIG. 2.

During manufacture of the bag 10, the circumferential or peripheral distance of the sidewall 14 is at the most equal to that ofthe bottom 16 so that the cross section of the sidewall is maintained in close conformity to the traylike configuration of the bottom wall 16 in plan view thereof.

The material of the sidewall 14 may be the normal thin thermoplastic, for example, .002 to .007 inch in thickness and the material ofthebottom wall may be substantially heavier in gauge, say in the region of .0l 2 inch or thicker, or it may be of the same thickness as the sidewall structure but in such a case it would be of a denser molecular structure to ensure rigidity greater than that of the sidewall.

FIGS. 3 to 10 disclose apparatus for forming the bags from two webs of thermoplastic materials. As it has been previously mentioned, this manufacture could advantageously take place in combination with a bag-loading line whereby the bags, after forming, would drop down onto a delivery belt which would carry them to loading mechanisms.

Referring to FIGS. 3 and 4, there is shown a supply of thermoplastic film I8, which may be preprinted and wound on a roll 20 that is rotatable through a spindle 22. The apparatus comprises a forming horn 24; a forming mandrel 26; and a sealing mechanism such as 28 or heater bar, not illustrated. In this first method, the film I8 is drawn off the roll 20, round the born 24 to be overlapped as shown on mandrel 26 which is then advanced by means of an air cylinder 30 towards position 8 and as this advancement takes place, the film is continuously drawn off the supply roll 20 and the overlap is heat sealed by the mechanism 28. When the mandrel 26 reaches position B, the bottom wall 16 is applied (FIG. 5) and the sidewall structure may be severed by a suitable cutoff mechanism 32, disposed at a position that is behind the mandrel when the latter is at position B. It will be appreciated, of course, that the cross-sectional configuration of the mandrel 26 adjacent its forward end constitutes the corresponding configuration of the formed sidewall of the bag 10. After the formed bag is severed from the supply roll by the mechanism 32 it may drop downwardly by gravity onto a delivery belt 34 or it may be assisted thereto by suitable mechanical means which is not illustrated.

The method of manufacture forms and seals together ofthe sidewall 14 and the bottom I6 from two separate webs of material. In accordance with the structure disclosed in FIGS. 5 to 7, a thermoplastic film I8 is drawn from the supply roll around a forming mandrel 44, which cooperates with a male and female mold adjacent its terminal end for applying the bottom wall I6 to the side wall of the bag. Furthermore, the male mold is provided with reciprocating means for working the mold towards and away from the end of the forming mandrel 44, which, in this case, is stationary. The formed bag is drawn along the forming mandrel by the male mold and severed from the next preformed bag by a variety of cutoff means which will be described in more detail hereinafter.

Briefly, it is schematically shown in FIG. 5 that the terminal end of the forming mandrel is provided with a female mold. The associated male mold, by means of a reciprocating frame structure (FIG. 6), brings a traylike bottom wall into engagement, about its periphery, with the peripheral terminal end edge of the sidewall structure of the bag preformed on the mandrel. The male mold is provided with an annular recess 66 so as to receive portions of the cutoff mechanism 64 that pass through the two layers of film constituted by the sidewall and bottom wall structure of the bag. After a bottom wall has been heat sealed to the sidewall structure, the male mold is withdrawn corresponding to the length of the bag desired and the cutoff mechanism is again actuated and the bag is dropped from the apparatus.

In FIG. 6, the forming horn 24 and film supply roll 20 together with .the seam-welding mechanism 28 have been omitted for the sake of clarity. A mold carriage 42 supports a stationary forming mandrel 44 which is of circular configuration at its starting end, but it gradually assumes the configuration of the desired bottom wall as it approaches the female mold 46, the specific configuration being provided by the latter.

Female mold 46 is resiliently mounted in axial alignment on the end ofthe mandrel 44 by studs 48 and springs 50.

A male mold 52 is mounted on the mold carriage in juxtaposition and in seriatim with female mold 46. The male mold 52 deforms and presses a portion of a second, preheated, web of material, W2, into the female mold 46 to form the bottom wall 16. Anair cylinder 54 is also provided on the mold carriage for axially reciprocating the male mold 52. FIG. 6 shows the molds in an operative position with the portion of the web W2 therebetween.

It will be seen that each mold is formed to provide a bottom wall I6 with an annular channel 56 adjacent its periphery and which is bounded on the extreme annular portion of the periphery by a header flat area 58 that is heat sealed to the sidewall I4 (see also FIGS. I and 2). This annular channel 56 is formed by an indented portion 60 in the female mold 46 and a corresponding protruding portion 62 in the male mold 52. Portion 62 is provided to allow annular insertion into the periphery of the male mold of cutoff mechanism 64 which must sever both the sidewall web 14 and the web W2 of the bottom wall material and the cutoff mechaniam 64 is received in a peripheral recess 66 (see also FIG. 5).

Male mold 52 is made up of a die 68 and die plug 70, the latter being connected to a venturi block 72 mounted on the mold carriage. Vacuum is applied through the venturi 72 to assist in forming the bottom wall 16 from the preheated web W2 and in cooperation with the male mold reciprocating means to effect the withdrawal of the formed bag from mandrel 44 through the reciprocating action ofthe air cylinder 54. When the withdrawal takes place, the cutoff mechanism 64 is again actuated to sever only the formed wall structure I4 from the remaining web on the mandrel which provides wall structure for the next bag in production.

The cutoff mechanism 64 is also mounted on the mold carriage by a mounting plate 76 (see FIG. 7) adapted to be secured to shafts 78 of the carriage adjacent the forming mandrel 44. The plate 76 includes a central opening or aperture 80 conforming to the configuration of the bottom wall I6 of the bag. This opening 80 is bounded by blades of cutoff knives 82 and 83, which are heated to effect the necessary seal between the two webs of material. Each knife, for example 82, is secured to a follower 84 which, in turn, is detachably connected to the piston rod of an associated air cylinder 86 that is suitably mounted to the plate 76. In accordance with actuation of the cylinders 86 the followers and their associated knives are adapted to reciprocate on guide pins 88 toward and away from the periphery of the bag structure and into and out of the recess'66 in the male mold 52. It will be seen from FIG. 6 that, at the time of severance and sealing of the two webs, the cutoff knives must be in radial alignment with the recess 66. Therefore, the cutoff mechanism is resiliently mounted, like the female mold 46, on a backup plate 90 which encircles the female mold as shown. The mounting is effected by studs 92 and springs 94 respectively. However, the direction of resilience is opposed with respect to the female mold 46.

The resilient mountings referred to allow axial shifting or humping" of the female mold and in order to prevent backward buckling of the tubular wall 14 on the mold 46 and mandrel 44,'vacuum is applied at 96 to hold the sidewall I4 in place while the female mold is axially moved by the male mold 52. As shown in FIG. 5, this allows frictional engagement between the end ofsidewall I4 and the peripheral flange I7 of the bottom 16 while it is being formed and places these two webs in position for heat sealing and severing.

It will be appreciated that, in a production run, the first bag would be manually fed into the apparatus. For the present description of the method it will be assumed that an initial bag has already been formed.

A first web 18 of material, at least on surface of which is scalable thermoplastic, is drawn from a supply about a forming horn and on to the main forming mandrel 44 where it is directed around the surface of the mandrel, overlapped, and seam welded together by the sealing means described in connection with FIG. 3 to thereby form the wall structure 14 of the bag I0. The reciprocating mold 52 gradually draws the tube 14 along the mandrel 44 until one end is over the female mold 46 which, at this stage, is in its outward position indicated by the peeked line C. In this outward position, the shoulders of the studs 48 engage the corresponding shoulders on the mold 46 through the action of the springs 50. Furthermore, it will also be appreciated that the male mold 52 is withdrawn sufficiently to allow insertion past the face of the female mold of web W2 of the material for forming the bottom wall 16. This web is also drawn from a supply (not shown) and its temperature is raised by known preheating means. The male mold 52 may be cooled so that, with the assistance of the vacuum, the web W2 will quickly conform to the configuration ofthe face ofthe mold 52 to form the rigid bottom I6.

Prior to the engagement of the molds, vacuum is applied to the sidewall structure 14 at 96. While the sidewall structure is so held, the male mold 52 is driven into engagement with the female mold 46 by the air cylinder with web W2 therebetween. When this engagement takes place, female mold 46 is pressed axially backwardly against the springs 50 and a similar action applies to the studs and springs of the cutoff mechanism so that the elements are in the position shown in FIG. 5. This engagement allows the overlap of the web W2 and the sidewall structure 14 as shown.

The cutoff mechanism is then actuated and the knives (or heated wires) are brought radially inwardly into the confines of the recess 66 thereby severing the bottom 16 from web W2 and heat sealing together the flange 17 on the bottom 16 with side wall 14 to complete the application of the bottom to the sidewall structure of the bag. The cutoff knives or wires are then withdrawn and the male mold 52 is subsequently withdrawn, vacuum being applied to the bot om 16, whereby the sidewall structure is drawn off the forn ing mandrel 44. The cutoff mechanism is then again actuattd in accordance with the length desired to form the comple e bag which drops from the apparatus.

It will be appreciated from the foregoing description of the apparatus and method for forming the bag in question, that the bottom wall 16 serves to retain the bag at its fullest periphery. Moreover, it is well within the scope of the present invention to apply the apparatus in combination with a loading and filling device for simultaneous operation. in such a combined operation, the center of the forming mandrel 44 would be hollowed out and used to direct produce into the center of the bag as it was formed. In such a case, the mandrel 44 could be oriented in a vertical position.

Although the cutoff mechanism described thus far is directed to knives that are heated to perform the sealing operation in combination with the cutting operation, it will be appreciated that heated wires or'other sealing and severing media could be used. FlGS. 8-l0 show two such embodiments. FIGS. 8 and 9 show a die having an impulse hot wire for sealing the webs forming the bag and a cold knife for cutting the second web. FIG. 10 shows a die having an impulse hot wire for sealing the webs and a second impulse hot wire for severing the second web peripherally around the base of the bag.

The inclusion of the impulse hot wire is preferably accompanied by minor modifications to increase the speed of operation of the machine and to prevent excessive heat build up. The back up plate 90 is provided with internal water-cooling tubes 99 which rapidly dissipate the heat generated by the impulse sealer 97 (FIGS. 8-10) and the impulse trimmer 101 (FlG. 10) which is located adjacent sealer 97 on the backup plate 90. The second web W2 is preferably held in a resiliently mounted peripheral guide 103 so that when the die is opened the second web W2 is withdrawn from the female die 46 to ensure ease of indexing. As the male form 52 advances, forming the bottom 16 of the bag 10 in the preheated web W2 the guide 103 is urged towards the backup plate 90 against the action of springs or hydraulic means 105.

in order to ensure close alignment of the webs l4 and W2 for sealing it is preferable that low pressure air l0 p.s.i. as an example) should be applied to the recess 66 by air line 98, and to facilitate withdrawal of the finished bag a vacuum is conveniently applied to the bottom 16 of the finished bag. Through the bores 107 from venturi 72 in the male die 52 a seal ring 109 is provided between the male die 52 and guide 103 to ensure against pressure leaks.

We claim:

1. Apparatus for manufacturing thermoplastic bags having a bottom wall more rigid in nature than its associated sidewall, comprising: 1

a. a forming mandrel adapted to receive therearound a first web of thermoplastic film to form a tubular sidewall structure for said bag;

b. a female mold resiliently mounted for limited axial movement on one end ofsaid forming mandrel;

c. a male mold mounted in juxtaposition with respect to said female mold, and being adapted to deform and press a portion of a second web of material into said female mold and into peripheral engagement with one end of said sidewall structure;

(1. meansfor reciprocating said male mold toward and away from said female mold; and

e. annular cutoff means adapted, when actuated, to sever said second web from the portion within said molds and simultaneously to heat seal said portion to said sidewall structure thereby to form said bottom wall.

2. Apparatus according to claim 1 including a peripheral recess in said male mold for receiving said cutoff means during the severing and sealing of said first and second web.

3. Apparatus according to claim 2 wherein said cutoff means comprises at least a pair of heated annular knives disposed normal and adjacent to said recess in the male mold.

4. Apparatus according to claim 1 wherein said male mold is adapted, upon pressing said second web into said female mold, to axially shift said female mold whereby a selected portion of the second web frictionally engages a terminal end edge of said sidewall structure on the forming mandrel.

5. Apparatus according to claim 4 including vacuum means associated with said mandrel adapted to retain said sidewall structure in position during shifting of said female mold.

6. Apparatus for-manufacturing thermoplastic bags in which the bottom wall thereof is more rigid in nature than the associated sidewall, said apparatus comprising a mold carriage supporting in longitudinal alignment:

a. a sidewall-forming mandrel adapted to receive therearound a first web of thermoplastic film to provide a tubular sidewall;

b. sealing means associated with said mandrel for seam welding said tubular sidewall;

c. a female mold resiliently mounted on one end of said mandrel for limited axial and longitudinal movement with respect thereto;

d. a male mold mounted in juxtaposition and seriatim with respect to said female mold and being adapted to deform and press a second web of material, normal to said tubular structure, into said female mold and to axially shift the latter;

e. means for axially reciprocating said male mold toward and away from said female mold;

f. annular cutoff means comprising at least a pair of heated annular knives adapted to .ever said second web from said molds and to annularly seal the molded second web to the tubular sidewall to form said bottom; and

g. vacuum means for holding said tubular sidewall in position during axial shifting of the female mold whereby a peripheral portion of the sidewall will engage said second web around said molds; the male mold including a peripheral recess therein adapted to receive said annular knives.

7. Apparatus according to claim 6 including further vacuum means associated with said male mold whereby the latter may draw said bottom and sidewall off said forming mandrel.

8. Apparatus for manufacturing thermoplastic bags having a bottom wall more rigid in nature than its associated sidewall, comprising:

a. a forming mandrel adapted to receive therearound a first web of thermoplastic film to form a tubular sidewall structure for said bag;

b. a female mold resiliently mounted for limited axial movement on one end ofsaid forming mandrel;

e. a male mold mounted in juxtaposition with respect to said female mold. and being adapted to deform and press a portion of a second web of material into said female mold and into peripheral engagement with one end of said sidewall structure;

d. means for reciprocating said male mold toward and away from said'female mold;

. heat seal means adapted to heat seal said second web within said molds to said sidewall structure thereby to form said bottom wall of said bags; and

f. cutoff means adapted, when actuated, to sever said second web from the portion within said molds. 9. Apparatus according to claim 8 wherein said heat seal means comprises a hot wire.

10. Apparatus according to claim 9 wherein said heat seal means comprises an impulse heated hot wire.

ll. Apparatus as claimed in claim 8 wherein said heat seal means is an impulse heated hot wire and said cutoff means is a cold knife.

12. Apparatus as claimed in claim 8 wherein said heat seal and cutoff means comprise an impulse heated hot knife. 

